Residents reported smelling smoke around 7 a.m., and many were trapped inside the four-story building in the 300 block of North Negley Avenue.

Smoke filled the stairwell and they were unable to escape. Firefighters had to use ladders and go window by window to pull more than two dozen residents to safety. (SLIDESHOW: Photos of the fire scene)

Aaron Patterson said he was sleeping when the fire started. "I opened up our window, and we had our heads just dangling out the window, signaling to people so that they knew that we were there," he said.

"I opened up my door, and there was black smoke billowing into my apartment. I freaked out," said another building resident, Mike Dodds.

Pittsburgh Fire Chief Darryl Jones praised the firefighters who braved the cold and snow to pull residents to safety. "Because of their efforts, this could have been a tragedy of humongous proportions," he said.

Residents said they were grateful to the men and women who risked their lives to save them.

"We ran to the closest window, and we was hanging out the window because the smoke was all in the room and we couldn't breathe, and that's when they had the ladder come up to the third floor and they brought us down," Everette Middlebrook said.

Four people were hospitalized for smoke-related injuries and about 10 more were treated at the scene.

Two animals were killed in the fire, and the ones that made it out were exhausted. The fire serves as a reminder that pets pay a price, too.

The Animal Rescue League saved four cats from the fire, three of which have been reunited with their owners.

"It's obviously missing its owner," said Dan Rossi of the Animal Rescue League as he cared for a cat that had been rescued. "We'd like to reunite them as soon as possible. We'll hang on to the guy until an owner comes forth."

Pittsburgh police say they used evidence lifted from Mocospace after the suspect uploaded acts to the site. The girl told police that he knew she was only 13 and that he would stalk and harass her, waiting for her to get off the school bus.